"Linux is not Windows, and although there are some similarities, you must realize that there may be a few 'new ways of doing things' to learn before you can be comfortable in Linux. Linux is an open-source clone of UNIX, a secure operating system that predates DOS and Windows and is designed for multiple users. The items in the following list generally apply to any UNIX-based *nix system, such as Linux and the various BSD's. For the purposes of this article, assume that it's all Linux."

I think many people misunderstand that image. On the left is a Linux filesystem tree and on the right a Windows one. The red lines indicate where on Linux (not Windows) that a particular directory might be mounted in relation to where the drive letters in Windows are. The lines should have arrow heads on the right side.

It is very common for Linux users to create a seperate partition for the home directory so that they can blow away the rest of the OS and still keep all their files safe.

In windows there is no true indication from that tree that D: is /dev/hdb or /dev/hda2 or something else.